Yellow Field Peas Fare Well After Recent Lows

May 4, 2017

Figures 1a (left) and 1b. Nebraska's crop of field peas escaped major frost damage from the recent cold spell due to its level of frost tolerance. (left) Field of field peas at the University of Nebraska-Lincoln High Plans Agricultural Lab near Sidney (Photo by Dipak Santra). (right) Field peas at the West Central REC near North Platte this week (Photo by Rodrigo Werle).

Most yellow field pea being grown in western Nebraska were at early vegetative stages (4^th to 7^th node or 1-5 leaf stages) during last week’s cold snap, but extensive damage is not expected due to the pea’s level of frost tolerance.

Field pea tolerance to frost during early stages of vegetative growth is partially due to the “hypogeal” germination nature of the crop. For plant species with hypogeal germination (e.g., field pea, lentil, chickpea), shoot germination occurs belowground. It is different from plant species with epigeal germination (e.g., soybeans and common beans) where shoot germination occurs aboveground and plants are sensitive to early season frost.

In pea, the growing point/cotyledons and 1^st node remain with the seed below ground. During the first three weeks after planting, the 2^nd and 3^rd nodes usually stay belowground and act as axillary buds. Pea can withstand extremely low temperatures (19–23^oF) between the 1^st and 5^th node stages (Figure 2), even in the absence of snow cover on plants.

If leaves are killed and the stem is wilted, new growth will emerge from underground axillary buds through the 5^th node stage. When plants are insulated by snow, they can tolerate temperatures as low as 10⁰F without much damage. If frost occurs when plants are at the 7^th node stage or beyond (40-50 days after planting, depending on weather conditions), plants are not likely to survive because axillary bud initiation will not occur at this stage.

field pea node illustration from Cornell University — Figure 3. Pea seedling showing 1^st to 5^th node. (Photo courtesy Cornell University)

Field peas at North Platte — Figure 4. Field peas in corn residue in Webster County (Photo by Strahina Stephanovic)

Field peas in corn residue — Figure 4. Field peas planted in corn residue (Photo by Dipak Santra)

Patience is needed when accessing suspected freeze injury. It will take at least one week of favorable weather for any freeze injury to be identified. Thus, don’t make any decision after a cold spell until the scope of the problem can be fully accessed.

As always, before destroying any crop consult the appropriate parties (crop insurance provider, Farm Service Agency, crop consultant agronomist, or UNL Extension educator).

Frost tolerance in pea is a complex process like drought tolerance and depends on the duration of acclimation/declamation cycles. When temperature drop is gradual, cold-acclimated field pea seedlings can tolerate significantly lower temperatures than when the temperature drop is sudden and hits non-acclimated field pea seedlings.